What you're asking is called the paradox of tolerance. It's a subset of Plato's paradox of freedom, and its refutations are roughly 30 seconds younger because it is based on a lie. Inclusivity is not an absolute axiom guiding all decisions. It is a priority applied equally across all individuals who value it. For individuals acting to undermine tolerance, the priority of fighting for the rights and freedoms of all take a higher priority position than the individual priority of tolerating individuals who disagree. Your freedoms and your rights end when they infringe on the freedoms and rights of others.
In other words, if you're an asshole, people who tell you to shut the fuck up are not the assholes. They're just trying to exist without having to deal with your bullshit. You're still the asshole, so shut the fuck up.
People say this a lot, but all I ever see in real life is someone being a huge asshole or spouting off some dog-whistle talking points while pretending to be "civil". They get shut down hard and go whining and complaining that the left was mean to them.
Sorry if I came off that way, because I'm legitimately curious about it. Don't a lot of people on the left, at least those online, also agree with this, though?
The idea comes up a lot, especially in response to the US right wing party circling the wagons around some new thing. I think conceptually some people wish the left could achieve the same kind of unity, but that's not what progressive politics look like. The constant pressure to reevaluate stances is the core feature, not a side effect of angry, online lefties. It should be a constant effort to look at the systems we have created and evaluate if they are promoting the common good. When they're not, and some people continue to promote them, that's an impasse.
Purity policing? Is that a city thing? Kinda sounds a lot like mike Johnson to me. Cause I regard myself as left of centre, and purity is a dirty concept to me. That being said, I grew up in a place that is pretty egalitarian but has questionable phrases like "yer no a man til ya shagged a tran!". Yay lady dick!
Because the Left always eats its own. Nothing is ever good enough, everyone must be equally miserable and cater to the lowest common denominator; complete mediocrity and underachievement is celebrated. Obviously to them some deserve to be more miserable, just never the ones doing the finger-wagging and calling you every -ist and -ism.
To sum up, a bunch of complete losers are trying to make people feel bad for being objectively better than they are.